News items

The Arctic’s frozen ground contains large stores of organic carbon that have been locked in the permafrost for thousands of years. As global temperatures rise, that permafrost is starting to melt, raising concerns about the impact on the climate as organic carbon becomes exposed. A new study is shedding light on what that could mean for the future by providing the first direct physical evidence of a massive release of carbon from permafrost during a warming spike at the end of the last glacial period.

Figuring out how far sea level rose during past warm periods in Earth’s history starts with a walk on the beach, a keen eye for evidence of ancient shorelines, and a highly accurate GPS system. The math isn’t as simple as subtracting the distance from the old shoreline to the water’s edge, though. As massive ice sheets retreated during past ice ages, their weight on the land below lifted and the land rebounded. On longer time scales, circulation within the Earth’s mantle has changed the shape and height of the crust, as well.

Along the walls of Oceanographer Canyon, fish dart in and out of colorful anemone gardens and sea creatures send up plumes of sand and mud as they burrow. Bill Ryan, an oceanographer at Columbia University’s Lamont-Doherty Earth Observatory, watched the scenes through the windows of a mini research submarine in 1978 as he became one of the few people to explore the seafloor canyons that President Obama has now designated a national monument.

Buried deep in seabed sediments off east Africa, scientists have uncovered a 24-million-year record of vegetation trends in the region where humans evolved. The authors say the record lends weight to the idea that we developed key traits—flexible diets, large brains, complex social structures and the ability to walk and run on two legs—while adapting to the spread of open grasslands. The study appears today in a special human-evolution issue of the journal Proceedings of the National Academy of Sciences.

In much of France and Switzerland, the best wine years are traditionally those with abundant spring rains followed by an exceptionally hot summer and late-season drought. This drives vines to put forth robust, fast-maturing fruit, and brings an early harvest. Now, a new study shows that warming climate has largely removed the drought factor from the centuries-old early-harvest equation. It is only the latest symptom that global warming is affecting biological systems and agriculture.

In the years before the Syrian conflict erupted, the region’s worst drought on record set in across the Levant, destroying crops and restricting water supplies in the already water-stressed region. A new study shows that that drought, from 1998-2012, wasn’t just the most severe in a century of record-keeping—it was the Levant’s most severe drought in at least 500 years and likely more than 900 years.

In an effort led by current and former Lamont Tree Ring Lab scientists, the N-TREND consortium (Northern Tree-Ring Network Development) was created to develop a global database of tree-ring research that improves on efforts for developing large-scale temperature reconstructions across the Northern Hemisphere.

A new study questions the popular notion that 10th-century Norse people were able to colonize Greenland because of a period of unusually warm weather. Based upon signs left by old glaciers, researchers say the climate was already cold when the Norse arrived—and that climate thus probably played little role in their mysterious demise some 400 years later. On a larger scale, the study adds to building evidence that the so-called Medieval Warm Period, when Europe enjoyed exceptionally clement weather, did not necessarily extend to other parts of the world.

The long history of severe droughts across Europe and the Mediterranean has largely been told through historical documents and ancient journals, each chronicling the impact in a geographically restricted area. Now, for the first time, an atlas based on scientific evidence provides the big picture, using tree rings to map the reach and severity of dry and wet periods across Europe and parts of North Africa and the Middle East year-by-year over the past 2,000 years.

A new study finds that the Horn of Africa has become progressively drier over the past century and that it is drying at a rate that is both unusual in the context of the past 2,000 years and in step with human-influenced warming. The study also projects that the drying will continue as the region gets warmer. If the researchers are right, the trend could exacerbate tensions in one of the most unstable regions in the world.

Ancient pollen grains that were floating in the air when mammoths roamed Southern California are providing new insights into historic droughts in the region, including how a series of mega-droughts between about 27,500 and 25,500 years ago changed the ecological landscape. A new scientific paper tracks these changes and suggests that warm ocean conditions similar to what we see off Southern California today fueled that 2,000-year stretch of droughts.

Over 40 years, the scientists of the internationally renowned Lamont Tree Ring Lab have hiked the continents in search of tree-ring records. They have documented droughts that stretched for hundreds of years, dated historic earthquakes and volcanic eruptions, and found in trees around the world evidence of how the planet cooled and then started warming. The Lab has expanded dendrochronology’s capabilities and becme a global leader in research, training and technology.

Trees can record centuries of history in their rings – changes in rainfall and temperatures, even evidence of fires sweeping through a region or the climatic impacts of volcanic eruptions. Annual rings are common in trees that experience seasonal climate variability and dormancy, but in the tropics, these records are rare. Now, for the first time, scientists have documented consistent annual tree rings in a native species on Hawai’i. The history recorded in the ring widths could improve our understanding of the climate in the eastern tropical Pacific, a region where much of the variability of the El Niño-Southern Oscillation (ENSO) originates.

In the first project of its kind, scientists are drilling deep into the bed of the fast-shrinking Dead Sea, searching for clues to past climate changes and other events that may have affected human history back through Biblical times and before.